FIG. 18 is a diagram showing a configuration of a conventional vanishing point detecting system as disclosed in Patent Document 1. Referring to FIG. 18, this conventional vanishing point detecting system includes a main control unit 1810, an image inputting unit 1820, an edge point detecting unit 1821, a line segment detecting unit 1822, a line segment selecting unit 1823, and a vanishing point estimating unit 1830. Operation of this conventional vanishing point detecting system is outlined below (for details, refer to a description in Patent Document 1).
The image inputting unit 1820 inputs an image that is a target for vanishing point detection.
The edge point detecting unit 1821 detects edge points in the image inputted to the image inputting unit 1820.
The line segment detecting unit 1822 detects line segments as consecutive point sequences of edge points detected by the edge point detecting unit 1821.
The line segment selecting unit 1823 selects line segments deemed to be effective in vanishing point estimation, among line segments detected by the line segment detecting unit 1822.
The vanishing point estimating unit 1830 estimates a vanishing point position from the line segments selected by the line segment selecting unit 1823.
Next, operation of the vanishing point estimating unit 1830 will be described below.
Since in general the vanishing point is defined as an intersection point of extensions of plural line segments, if consideration is given to positional relationships of the two end points of each line segment and a vanishing point, it is considered that ideally 3 points (the two end points of a line segment and the vanishing point) are on a line. At this time, the area of a triangle formed by the two ends of the line segment and the vanishing point is 0.
Consequently, as shown in FIG. 19, the sum for all line segments of areas 1930 formed by the two end points of each line segment 1920 and the vanishing point 1920 is obtained, and a position at which this sum of triangular areas is at a minimum is estimated to be the vanishing point position. This estimation calculation can be performed analytically.
[Patent Document 1]
JP Patent Kokai Publication No. JP-P2005-275500A